1. Field of the Invention
This invention relates to a process for the manufacture of catalysts for the reduction of nitrogen oxides in exhaust gases or for chemical air cleaning processes, in which process catalyst moldings are manufactured from iron oxide or mixtures of iron oxide and chromium oxide and/or manganese oxide, possibly with the addition of measured quantities of activating additives, using sulfuric acid and phosphoric acid, and to catalysts manufactured according to the process.
2. Description of the Prior Art
The prior art includes processes for the manufacture of catalysts for the reduction of nitrogen oxides in exhaust gases or for chemical air cleaning processes, whereby in the reduction of nitrogen oxides from exhaust gases, NH.sub.3 is added to these exhaust gases for the chemical reaction of the nitrogen oxides with the ammonia, to form nitrogen.
U.S. Pat. No. 4,742,036 issued May 3, 1988 and entitled "Catalyst Plate" describes catalysts for the reduction of nitrogen oxides in exhaust gases, which contain as the principal ingredient a granular Fe.sub.2 O.sub.3 catalyst material and a binder, whereby this binder is phosphoric acid in a first mixture with the Fe.sub.2 O.sub.3 and sulfuric acid in a second mixture with Fe.sub.2 O.sub.3. These two mixtures are mixed with one another, and catalyst plates are manufactured from the resulting mixture.
U.S. Pat. No. 4,695,559, issued Sept. 22, 1987 and entitled "Catalyst for the Selective Reduction of Nitrogen Oxides in Waste Gases and Process for the Manufacture and Use of Such a Catalyst" describes a process for the manufacture of similar catalysts, in which iron oxide and chromium oxide as well as activating additives are mixed dry. This dry mixture is bonded with phosphoric acid, and then saturated with sulfuric acid. A calcining or tempering treatment is conducted and the moldings are then manufactured.
3. Cross-Reference to Copending Applications
U.S. patent application Ser. No. 94,081, filed Sept. 4, 1987 now U.S. Pat. No. 4,806,427, and entitled "Process for the Production of Catalysts for the Reduction of Nitrogen Oxides from Exhaust Gas and Similar Chemical Air Cleaning Processes" describes a process for the production of catalysts for the reduction of nitrogen oxides in exhaust gases, in which a catalytically active oxide mixture of iron or chromium ore and liquefier is prepared with water and sulfuric acid into a slicker, which is then applied to a metal carrier previously treated with an etching acid.
U.S. patent application Ser. No. 938,518, filed Dec. 5, 1986, now U.S. Pat. No. 4,758,545, and entitled "Process for the Manufacture of Catalysts Moldings from Granular Catalyst Material Such as Iron Ore or Chromium Ore with the Use of a Binder" also describes a process for the manufacture of catalyst moldings of iron, chromium or similar ores, using a binder, whereby the granular primary ores are first subjected to a thermal pretreatment at temperatures from approximately 250.degree. C. to 1000.degree. C., before they are mixed with dilute and/or concentrated sulfuric acid as a binder and reprocessed into catalyst moldings.
U.S. patent application Ser. No. 231,702 entitled "Process for the Manufacture of Catalytic Elements and Catalytic Elements so Produced" was filed on Aug. 12, 1988, which corresponds to German Patent Application No. P 37 27 118.0 filed on Aug. 14, 1987 which is entitled in English translation "Process for the Manufacture of Catalysts for the Reduction of Nitrogen Oxides in Exhaust Gases or for Chemical Air Cleaning Processes, and Catalysts Manufactured According to the Process".
All of the above-mentioned U.S. patents and applications are hereby expressly incorporated by reference as if the contents thereof were set forth in full herein.